1. Field of the Disclosure
The present disclosure relates generally to an aerial vehicle, e.g., an unmanned aerial vehicle (UAV).
2. Description of the Related Art
In general, a UAV flies by being guided by radio waves, according to a previously input program, or by recognizing and determining a surrounding environment (an obstacle, an air-way, etc.) and navigating through the determined environment by itself. The UAV may also be referred to as a “drone”.
A UAV equipped with an optical sensor, an infrared sensor, a radar sensor, etc., may be utilized for military purposes, such as surveillance, reconnaissance, guiding a precision weapon, and communication/information repeating. Further, a UAV may be used in the private sector to monitor and prevent accidents or mishaps, monitor geographic and environmental changes, conduct research and development, image capture, ship items, communicate, etc.
As private recreational UAVs have appeared in addition to those for use in the private sectors including image capturing, shipping (such as parcel-shipping), communication, etc., the demand for the convenience of movement and storage of UAVs has increased. However, a rotary wing UAV having a rotor or a propeller occupies a considerably wide space when the blades of the propeller are expanded, which may make the UAV difficult to move and/or store.
In order to facilitate the movement and storage of the rotary wing UAV, a propeller having blades that are foldable to be parallel with a propeller rotation axis and a propeller having blades that are foldable to be parallel with each other at one side thereof have been proposed. However, when the blades are folded in parallel with the propeller rotation axis, it is still difficult to store the UAV because the storage space still must accommodate the length of the blades in the direction of the rotation axis. While the blades that are folded to be parallel with each other at one side thereof may facilitate the movement or storage because the blades may be positioned on another structure of the UAV in the folded state, when the propeller rotates, the blades may not maintain a correct position on the propeller (e.g., a position at which the blades are aligned on a 2-blade propeller) due to a drag acting on the blades. For example, when the blades are folded to be parallel with each other at one side thereof, the rotational radius of the propeller may vary depending on an operating state, such that the propeller may suffer from a difficulty in properly exhibiting the designed performance of the UAV.